Chemical sterilizing apparatus



Dec. 19, 1961 F. G. LEUTHNER 3,013,573

CHEMICAL STERILIZING APPARATUS Filed June 22, 1959 6 Sheets-Sheet 1 FIG. I

INVENTOR.

FRANK G. LEUTHNER BY Am 3* Dec. 19, 1961 F. e. LEUTHNER CHEMICAL STERILIZING APPARATUS 6 Sheets-Sheet 2 Filed June 22. 1959 INVENTOR. FRANK G. LEUTHNER Dec. 19, 1961 F. G. LEUTHNER 3,013,573

CHEMICAL STERILIZING APPARATUS Filed June 22, 1959 6 Sheets-Sheet 3 FIG. 3

INVENTOR.

FRANK G. LEUTHNER Attorney Dec. 19, 1961 F. e. LEUTHNER 3,013,573

CHEMICAL STERILIZING APPARATUS Filed June 22. 1959 6 Sheets-Sheet 4 N g n 55 Q o -I b \o, Y, (\I N N N INVENTOR.

FRANK G. LEUTHNER Dec. 19, 1961 F. s. LEUTHNER 3,013,573

CHEMICAL STERILIZING APPARATUS Filed June 22, 1959 6 Sheets-Sheet 5 250 25l RELACE l REPLACE CYLINDER CYLINDER TO sramuzzn FIG. 6

INVEN TOR. FRANK G. LEUTHNER e sheets-sheet 6 Filed June 22. 1959 INVENTOR FRANK G. LEUTHNER F GE United States Patent Ofihce 3,013,573 Patented Dec. 19, 1961 3,013,573 CHEMKQAL STERHJZKNG APPARATUS Frank G. Leuthner, Gates, N.Y., assignor to Wilmot Casge Company, Brighton, NY, a corporation of New ork Filed lune 22, 1959, Ser. No. 322,tl65 Claims. (Cl. 137-1l3} This invention relates to chemical sterilizing apparatus, and more particularly to apparatus and a system for controlling the supply of chemical sterilizing agent to a sterilizer or to a storage tank for the same.

Chemical sterilization has been found to be very effective in the sterilizing of articles and products which were diiiicult or impractical to sterilize byconventional high temperature steam sterilization. One elfective chemical sterilizing agent is ethylene oxide mixed with carbon dloxide or with Freon. The sterilizing agent is commercially supplied in pressure cylinders, which contain the chemicals under high pressure.

Conventionaliy, in sterilization with gas, such as ethylone oxide, the gas was supplied from a. portable pressure cylinder in which the gas in a liquefied state was trans: ported. Where a large sterilizer was employed, the practice was to couple the cylinder to a storage or expansion tank from which the gas was supplied to the sterilizing chamber. In the case of smaller sterilizers and particularly in the case or conversion units, that is, where a steam sterilizer was converted for use of gas, it has been the practice to connect to the sterilizer, a control unit, and supply the, gas from the cylinder direct to the sterilizing chamber under control of this unit. In either case therehas been a danger of the ineffective sterilization of products because of running out of gas either from the expansion tank or from the supply cylinder in the middle of a. sterilizing operation.

One object or the present invention is to provide a plural source or" supply to either an expansion tank or a sterilizing chamber for supplying the tank or chamber successively from a plurality of supply cylinders.

Another object of the invention is to provide a system for controlling a plurality of, supply cylinders so that when the supply or" gas from one cylinder is exhausted the other cylinder is automatically cut in.

Another object of this invention is to provide apparatus for connecting a plurality of cylinders containing a chemical sterilizing agent to a sterilizer wherein a depleted cylinder may be replaced. without interrupting the operation of the sterilizer.

Another object of the invention is to provide a system for controlling the supply from a plurality of transportable cylinders whereby when the pressure in an expansion tank or in a sterilizing chamber drops below a practical operating pressure, one of the supply cylinders is automatically put on supply to thetank or the sterilizing chamber.

A still further object of this invention is to provide a control system for a chemical sterilizing supply apparatus, which indicates when a new supply of chemical is required.

Other objects, purposes, and characteristic features of this invention will be apparent from the accompanying drawings, the specification, and the appended claims.

in the drawings:

1 is a view of apparatus constructed according to one embodiment of the invention for controlling the supply of a sterilizing agent to an expansion and storage tank;

FIG. 2 is a front view of the control box of this apparatus, showing the various gauges thereon;

FlG. 3 is a fragmentary side view of the control box iii takenat line 3-3 of FIG. 2 and looking in the direction of the arrows;

FIG. 4 is a plan view with the cover removed, showing the arrangement ofthe interior mechanism of the control box;

FIG. 5 is a diagrammatic view of the electric circuitry of this control apparatus;

6 is a front view of a modified control box as: sembly for controlling the admission of a chemical sterilizing agent directly into a chemical sterilizer;

PEG. 7 is a plan view with the cover removed showing the arrangement of parts in the modified control box of FIG. 6; and

FIG. 8 is a diagrammatic view of the electric circuitry Of this modified apparatus.

in one embodiment of this invention the control apparatus is adapted to control the supply of a chemical from high pressure cylinders in which the liquified' gas is transported into an expansion tank which is connected to a sterilizing chamber. In the other embodiment of the invention, the control apparatus is adapted to control the supply of the chemical from the high pressure supply cylinders directly into a chemical sterilizing chamber. In both embodimcnts, high pressure supply cylinders containing a chemical sterilizing agent such as a carbon dioxide and ethylene oxide mixture, or a Freon and ethylone oxide mixture may be used.

Referring to the embodiment shown in NOS. 1 through 5 and and particularly to FIG. 1, lil denotes an expansion or storage tank. The sterilizing agent is supplied to the tank from conventional high pressure, replaceable shipping cylinders such as denoted at S and 9. Each contains the ethylene oxide and carbon dioxide or Freon mixture. They are connected to a control box assembly 7 which serves to control the introduction of the chemical into the expansion tank it).

The expansion tank ltl is provided in its lower portion with a heat exchanger assembly ll, which. comprises a steam supply valve 12 for admitting steam under pressure through a strainer 28 into a steam pressure reducer 13. The pressure reducer '13 leads to a steam gauge 14 which indicates the pressure of the steam entering the intake side of a solenoid operated valve- 15. The solenoid valve 15 when open admits steam to the interior of a tinned coil heat exchanger to inside the expansion tank it The steam exhausts from the coil '16 vinto a steam trap 13. heating the contents of the expansion tank 10, it isundere stood that any heating medium which can be accurately controlled, maybe utilized. 7

The cylinders 8 and 9 are attached by means of flexible conduits l8. and 19 to the control box assembly7. The,

control box assembly 7 is attached to the tank 10 by a threaded union Zl. Near the lower end of the-tank 10 is a manually-operable valve 22 which is provided with a suitable connection, and controls the introduction ofthe gas to a sterilizer (not shown). Near the upper end of the tank id is a blow off valve 23. 7

Referring to-FlGS. 2, 3 and 4, the flexible conduits l 8 and 19 leading from the pressure cylinders 8 and 9, re-. spectively, are threadably secured to the input of suitable filters 24 and 44), respectively, which are connected by pipes 25 and ll with manifolds 2d and 42, respectively. These in turn are connected by piping 27 and 43 with the intake of solenoid-operated regulating valves 28 and 44; These regulating valves 28 and 44 control flow of the gas through shutefi valves 33 and 49, respectively, which are connected through tubing 34 and 5t respectively, to a T 35. The T 35 is connected by tubing 35 (FIG. 3) through a'needle valve 37 and the unionil to the expansion tank 10.

Although a. steam heat exchanger is used for Standard pressure switches 29 and 45 are operatively connected to the coils of the solenoids which operate valves 28 and .4, respectively, so that these switches control the opening and closing of the valves 28 and 44, respectively, by energizing or deenergizing the solenoid coils. The pressure switch 29 is connected to manifold 26 by tubing 31 and 32. The pressure switch 45 is connected to manifold 42 by tubing 47, 48. In this embodiment the pressure switches 29 and 45 permit the respective solenoid valves 28- and 44 to open only when the pressure in either cylinder 8 or 9 is above a predetermined pressure, three hundred pounds, for example.

Gauges 3t) and 4-6, respectively, are provided to indicate the actual pressure in the cylinders 8 and 9 at ail times. The indicator gauges 3% and 46 are operably connccted to respective manifolds 26 and 42 by means of tubing 31 and 47, respectively. The shutofi valves 33 and 49 are manually operable to shut ofi the supply of chemical from cylinders 8 and 9, respectively, to the expansion tank 16 at times when the apparatus is not being used.

An indicator 51 is provided to indicate the gas pressure in the expansion tank 10 at all times. This is operably connected by means of a conduit 52 to a pressure manitold 53 which is at the same pressure as the expansion tank 10. The manifold 53 is in communication with the tank it; through the union 21, a needle valve 54 (FIG. 3) and the curved conduit 55. Also connected to the manitold 53 and controlled by the gas pressure in expansion tank it: is a pressure switch 56 (FIG. 4) which is provided with a contact 57 (see FIG. which is adapted to be closed when the pressure in the tank is below a predetermined pressure, eighty pounds, for example, and is adapted to open when the pressure in the tank is above a predetermined pressure, one hundred thirty pounds per square inch, for example. Each one of the pressure switches 29, 45 and 56 are provided with an adjusting means 6%, 61 and 62 (FIG. 2), respectively, to adjust the operation of its respectively associated switch in accordance with the desired critical pressures in the supply cylinder 8 or 9, and the expansion tank 10, as the case may be.

There is also provided on the front of the control box 7 a warning lamp 64 which is illuminated when the pressure in both cylinders 8 and 9 is below the required minimum. A conventional manually-operable switch 65 is provided to turn the apparatus on or off. A lamp 66 is provided which is illuminated when the switch 65 is in its on position. An adjustable thermostat 70 is manually regulable to control the temperature of the gas in the expansion tank It). The thermostat 7! has a temperature sensitive element 71 (FIG. 5), which is in communication with the interior of the tank 10 by means of a conduit 73 (FIG. 1).

In use, the thermostat 70 is set at the desired temperature, for example one hundred ten degrees. The valves 33 and 49 are turned on; and the switch 65 is turned to its on position thereby illuminating the lamp 66. Steam is admitted through the valve 12, the solenoid valve 15, and into the coil 16.

Referring to FIG. 5 and assuming that the pressure in the expansion tank 10 is below say, a desired pressure of eighty pounds per square inch, the contact 57 of the pressure switch 56 is in its full line closed position. Also, assuming that fresh cylinders 8 and 9 are connected to tank 10, which have a standard pressure of say six hundred fifty pounds per square inch in each cylinder, contacts 91 and 92 of the pressure switches 29 and 45, respectively, are in their closed left-hand positions (as viewed in FIG. 5). Also, assuming that the temperature of the expansion tank 10 is below say the one hundred degrees Fahrenheit required, and the temperature is set for one hundred ten degrees Fahrenheit, the contact '71 of the regulator 76 is in its closed position.

When the switch 65 is moved to its on position, the solenoid coil of the valve is energized, to admit steam into the heating coil 16, by a circuit which extends from L1 and includes contact 83 or switch 65 in its left-hand position, the now-closed contact 7i, and the winding of the solenoid valve 15 to GR. The lamp 66 is also illuminated by a circuit which extends from Li and includes the lamp 66 to ground GR. Simultaneously, with the closing of the switch 65, a circuit is completed for energizing the solenoid of the regulating valve 28, thereby admitting the gas mixture or chemical from cylinder 8 into the expansion tank 16. This circuit extends from L1 and includes contact 83 of switch 65 in its left-hand position, contact 57 of. the pressure switch 56 in its closed position. contact 91 of the pressure switch 29 in its left-hand position, and the winding of the solenoid valve to ground GR.

Assuming that the pressure in the expansion tank 10 increases to the desired predetermined pressure of one hundred thirty pounds per square inch, for example. the contact 57 of the pressure switch 56 opens, thereby interrupting the energizing circuit for the solenoid coil of valve 28, which shuts off the valve 28, and cuts off the supply of chemical from the cylinder 3 to the expansion tank It).

When the gas in the expansion tank 10 reaches the required temperature, the thermostatic element 7% opens its contact 71, thereby deenergizing the solenoid coil, which operates the steam valve 15, to cut off the supply of steam to the interior of the tank it], thereby preventing further heating of the gas in the expansion tank. Thus. it is seen that when the temperature in the tank falls below the adjusted selected temperature of say, one hundred ten degrees Fahrenheit, the contact 71 will close to open the valve 15. It is also apparent that when the pressure in the expansion tank falls below the selected minimum of say, eighty pounds per square inch, the contact 57 of the valve 56 will close thereby opening the regulating valve 28 to admit an additional supply of chemical into the tank 10.

Now assuming that the apparatus has been operating for some time, and the pressure in the cylinder 3 falls below the required three hundred pounds per square inch, the contact 91 of the pressure switch 29 moves to its right-hand closed position. This shuts off cylinder 8. When the pressure in the expansion tank 10 falls below eighty pounds per square inch, because of drain of the sterilizer on the expansion tank, the contact 57 will move to its closed right-hand position, thereby energizing the solenoid of the valve 44 and opening the valve 49 to admit the chemical mixture from the supply cylinder 9 into the expansion tank It}. The circuit for opening valve 44 extends from L1 and includes contact 83 of switch 65 in its left-hand position, contact 57 of pressure switch 56 in its right-hand position, contact 91 of pressure switch 29 in its closed right-hand position, contact 92 of pressure switch 45 in its closed lef -hand position, and the solenoid winding of the valve 44 to ground GR. The expansion tank 10 is now receiving the chemical from the supply cylinder 9.

Thus it is seen that when cylinder 8 has a pressure of say, less than three hundred pounds per square inch, and cylinder 9 has a pressure of say, greater than three hundred pounds per square inch, the expansion tank 10 is supplied with the chemical from cylinder 9.

Assuming that the system has been operating for some time, and the pressure in the supply cylinder 9 has fallen below three hundred pounds per square inch, the contact 92 of the pressure switch 45 assumes a right-hand closed position, thereby breaking the circuit to the solenoid valve 44. This shuts off cylinder 9 and illuminates the warning lamp 64. The circuit for illuminating the lamp 64 extends from the closed contact 2 of the pressure switch &5 in its right-hand position through lamp 64 to ground At this point, the supply cylinders 8 and 9 are removed, and new supply cylinders are put in their place. Instead of waiting until both cylinders 8 and 9 are depleted, however, it is obvious from the preceding description that a fresh supply cylinder 8 may be connected to the conduit 18 while supply cylinder u still has the required pressure and vice versa.

Reference will now be made to the modification of the invention shown in FIGS. 6 to 8 inclusive. Parts in this modification, which are identical with the embodiment shown in FIGS. 1 to 5, inclusive, are identified by the same reference numerals. In this modification of the invention the sterilizing agent is supplied directly to a sterilizing chamber from the conventional replaceable shipping cylinders, such as 8 and 19. These cylinders are here attached by the fiexibleconduits 18 and 19 to control box assembly 297 which controls the flow of the chemical.

The fiexib-le conduits 18 and 19 are threadably secured to suitable input filters 24- and 40, respectively, which are connected by pipes 25 and 41, respectively, with manifolds 26 and 42, respectively, similar to the previously described embodiment. These manifolds in turn are connected by piping 27 and 43, respectively, with the intake of solenoid operated valves 28 and 44, respectively, which control the flow of the chemical from the cylinders 8 and g into a sterilizing chamber (not shown). As in the previous embodiment, standard pressure switches 29 and d selectively open and close valves 28 and 44, respectively, by energizing or deenergizing the windings of the solenoids which operate these valves. The pressure switches 29 and 4d respond to the actual pressure of the cylinders 8 and 9, respectively, that is when the pressure in cylinder 8 is over three hundred pounds, for example, contact 91 (FIG. 8) of pressure switch 29 is in its closed right-hand or solid line position. When the pressure in cylinder 8 is below three hundred pounds, for example, contact 91 of pressure switch 29 is in its closed left-hand or dotted line position. When the pressure in cylinder 9 is above three hundred pounds, for example, contact 92 of pressure switch 45 is in its closed left-hand or solid line position; and the contact 92 is in its closed righthand or dotted line position when the pressure in the cylinder 9 is below three hundred pounds.

As in the previous embodiment, the gauges 3i) and 46 re provided to indicate the actual pressure in thecylinders 3 and 9, respectively, and the output of the regulating valves 28 and 44 lead through manually-operated shut off valves 33 and 49, respectively, which are connected through tubing 34 and 50, respectively, to the T 35. The "s" 35 is connected by tubing 236 to the sterilizing chamber of a sterilizer.

A pressure switch 256 is provided with a contact 257, (MG. 8) W1. ich is adapted to close when the pressure of the sterilizing chamber is below say eighteeen to twenty five pounds, for example, and is adapted'to open when the pressure in the sterilizing chamber is above such a pressure. In the event that Freon and ethylene oxide mixture is used the operating pressure in the sterilizing chamber is lower such as eight to nine pounds, for example, and the pressure switch 256 is adjusted accordingly.

It has not been considered necessary to show all of the controls for the sterilizer. Suffice it to say that when a point is reached in the sterilizing cycle which calls for admission of the gas into the sterilizing chamber a cycle control switch 275 is closed. This switch has a contact 276.

Located in the front of the control box 207, is a lamp 255%, which is illuminated when the pressure cylinder 8 is below three hundred pounds, for example, and a lamp 251, which is illuminated when the pressure in cylinder 9 is below three hundred pounds, for example. The lamp 66 is illuminated when the sterilizer is turned on.

A latching relay assembly, generally referred to as 260, serves in. this embodiment to control switching from cylinder 8 to cylinder 9 for supply, and vice versa. This relay assembly comprises a pair of relays 262 and 264. The relay 2:52 is provided with contacts 27%) and 271. contact 27 is closed and the contact 271 is opened when the winding of the relay 262 is energized. The relay 264 is provided with contacts 272 and 273. The contact 272 is closed at 274 and the contact 273 is open when the relay 264 is energized. When the relay 264 is deenergized the contact 273 is closed, and the contact 272 makes contact at 275. This is the position shown in FIG. 8. The latching relay assembly may be of conventional construction and the relays are so connected, either mechanically or electrically that when one relay is energized the other relay is deenergized. Also when the deenergized relay of the assembly kicks in orbecomes energized the previously energized relay kicks out. This causes only one or the other of the relays 2 62 and 264 of the latching relay assembly 26% to be energized at a time.

Now assuming that a sterilizing cycle iscom-menced in the sterilizer, the apparatus is turned on by a switch (not shown) thus illuminating lamp 65. Atthis time, the pressure in the sterilizing chamber is below the eighteen to twenty-five pounds thus causing the contact 257 of the pressure switch 256 to be closed. When the point in the cycle is reached when the sterilizing gas should be introduced into the chamber, a Contact 276 of switch 275 is closed which completes a circuit for energizing the solenoid for operating the regulating valve 28 associated with the cylinder S'tlius permitting the sterilizing gas to enter the sterilizing chamber through the pipe 236. The circuit for energizing the winding of the regulating valve 28 extends from and includes the winding 262 of one latching relay, front con.- tact 27d of this latching relay, contact 275 of the relay 264, closed contact 276 of the cycle switch 275, closed contact 257 of the pressure switch in the sterilizing chamber, contact 273 of the relay 264 and the winding of the solenoid valve 28 to The sterilizing gas continues to enter the sterilizing chamber until the pressure of from eighteen to twentyfive pounds is reached at which time the contact 257 opens thus interrupting the previously described energizing circuit to the solenoid valve 28. This shuts off cylinder 8. The gas will be introduced into the sterilizer for a predetermined length of time, according to conentional practice, and when the timer (not shown) Which controls this length of time, times out, the contac 276 opens.

It should be noted that if the gas in both cylinders 8 and 9 is above minimum working pressure, an e ner giz ing circuit is complete for both the relay windings 22 and relay 264 because of the position of the pressure switches 29 and 45. ,However, as only one latching relay can be picked up or kicked in at one time only the relay 262 is energized at the start of the operation.

Now assuming that the pressure in the cylinder '8 falls below three hundred pounds per square inch, the contact 91 of the pressure switch 29 shifts to its dotted line position thus causing the. relay 262 to kick out and the relay 264 to kick in. This conditions cylinder 9 for supply and decon ditions" cylinder 3. When the sterilizing apparatus reaches that point in its cycle which calls for sterilizing gas the contact 276 and the contact 257 are closed, thus energizing the solenoid of the regulating valve 44 to permit the gas from the cylinder 9 to enter the sterilizing chamber by a circuit which extends from and includes the winding 264, contacts 272 and 274, now-closed contact 27'ttfnow-closed contact 257, contact 271 of the winding 262 and the winding of the valve 44 to r In this position the warning lamp 250 is illuminated, thus notifying the operator to replace the cylinder 8. When a new cylinder is attached to the conduit 18, the pressure switch 29 is then actuated so that its contact 91 assumes its solid line right-hand position. However, as the latching relays will not shift their position until the now-energized relay 264' becomes deenergized by the shifting of contact 92, the gas'will continue to be drawn as needed from cylinder9 until its pressure falls below the required three hundred pounds.

When the pressure in thecylin'der 9 does fall below the workable minimum, contact 92 shifts, but relay 262 will not be reenergized until relay 264 has been deenergized, thus unlocking relay 264 and locldn relay 262.

Thus, I have provided in this second embodiment of the invention a supply apparatus which alternately shifts from one supply cylinder to another as the supply be comes exhausted. It is apparent that the sterilizing cycle never has to be interrupted and that if the operator installs a new cylinder 8 or 9 when the warning lamp 250 or 251 is illuminated, the sterilizing apparatus will always have an adequate supply of the sterilizing chemical connected thereto.

Although a carbon dioxide and ethylene oxide mixture, and a Freon and ethylene oxide mixture have been mentioned for use with both embodiments of this apparatus, it is intended that it may be used with any type of chemical sterilizing agent. Furthermore, the critical pressure mentioned in the use of the apparatus herein has been those that would normally be used for the carbon dioxide ethylene oxide mixture. It is apparent that where Freon and ethylene oxide or some other chemical is used that various pressure switches may be altered to introduce the chemical and to shut it off at other required pressures.

While the invention has been described in connection with a specific embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. An apparatus for controlling the supply of a volatile chemical sterilizing agent to a vessel, comprising means for connecting a first chemical supply cylinder to said vessel including a first valve, a first pressure switch operated in response to a selected minimum pressure in said first cylinder, means for connecting a second chemical supply cylinder to said vessel including a second valve, a second pressure switch operated in response to a selected minimum pressure in said second cylinder, a vessel pressure sensing means movable to an operating position only when the pressure in the vessel is below a predetermined amount, means responsive to the vessel pressure sensing means in its operative position when the first pressure switch is in its operated position for opening said first valve, and means responsive to the first pressure switch in its unoperated position and the second pressure switch in its operated position when the vessel pressure sensing means is in its operated position for opening said second valve.

2. An apparatus for controlling a supply of a volatile chemical sterilizing agent to a vessel, comprising means including a first valve for connecting to said vessel 21 first source of chemical under pressure, means including a second valve for connecting to said vessel a second source of chemical under pressure, a first pressure switch connected to said first source operable to be closed when the pressure from said first source is below a predetermined amount, a second pressure switch connected to said second chemical source and operable to be closed when the pressure from said second source is below a predetermined amount, a third pressure switch operably connected to said vessel and operable to be closed when the pressure in said vessel is below a predetermined amount, means responsive to the closing of said third pressure switch when said first pressure switch is open to open .said first valve to admit chemical from said first supply source into said vessel, and means responsive to the closing of said first pressure switch when said third pressure switch is closed and said second pressure switch is open :for opening said second valve to close off said first chemit3 cal source and connect said second chemical source to said vessel.

3. An apparatus for controlling the supply of a volatile chemical sterilizing agent to a vessel, comprising means for connecting a first source of chemical supply to said vessel, means for connecting a second source of chemical supply to said vessel, a first pressure switch being in one position in response to more than a predetermined pressure from said first source and being in another position in response to less than a predetermined pressure from said first source, a second pressure switch being in one position in response to more than a predetermined pressure from said second source and being in another position in response to a lower than a predetermined pressure from said second source, a third pressure switch which closes in response to less than a predetermined pressure in said vessel, a first valve having a soleacid which when energized opens said first valve to admit the chemical from said first source into said vessel, a second valve having a solenoid which when energized opens said second valve to admit the chemical from said second source into said vessel, a source of energy, a first circuit means including said source of energy responsive to the closing of the third pressure switch when the first pressure switch is in its said one position for energizing the solenoid of the first valve, and a second circuit means including said source of energy responsive to the closing of the third pressure switch when the first pressure switch is in its said other position and the second pressure switch is in its said one position for deenergizing the solenoid of the first valve and energizing the solenoid of the second valve.

4. Apparatus for controlling the supply of a chemical sterilizing agent to a sterilizer, comprising an expansion tank, means including a first valve for connecting to said tank a first source of chemical under pressure, means including a second valve for connecting to said tank a second source of chemical under pressure, a pressure switch connected to said first source operable to be closed when the pressure from said first source is below a predetermined amount, a second pressure switch connected to said second source and operable to he closed when the pressure from said second source is below a predetermined amount, a third pressure switch connected to said expansion tank and operable to be closed when the pressure in said tank is below a predetermined amount, means responsive to the closing of said third pressure switch when said first pressure switch is open to open said first valve to admit chemical from said first supply source into said tank, and means responsive to the closing of said first pressure switch when said third pressure switch is closed and said second pressure switch is open for opening said second valve to connect said second source to said expansion tank.

5. An apparatus for controlling the supply of a volatile chemical sterilizing agent to a vessel, comprising means for connecting a first chemical supply cylinder to said vessel, means for connecting a second chemical sup ply cylinder to said vessel, a first pressure switch being in one position in response to more than the predetermined pressure from said first cylinder and being in another position in response to less than a predetermined pressure from said first cylinder, 21 second pressure switch being in one position in response to more than the predetermined pressure from said second cylinder and being in another position in response to a lower than a predetermined pressure from said second cylinder, a third pressure switch being in one position in response to less than a predetermined pressure in said vessel and being in another position in response to more than a predetermined pressure in said vessel, 21 first valve having a first solenoid which when energized opens said first valve to admit the chemical from said first cylinder into said vessel, a second valve having a solenoid which when energized opens said second valve to admit the chemical from said second cylinder into said vessel, a source of energy, a first circuit means including said source of energy when said first pressure switch is in its one position and said third pressure switch is in its one position for energizing the solenoid of said first valve, a second 5 open said second valve, and means responsive to the 10 2402187 shifting of said second pressure switch to its other position when said first and third pressure switch is in its one position for completing said first circuit means to energize said first solenoid to open said first valve.

References Cited in the file of this patent UNITED STATES PATENTS Seat Oct. 4, 1938 Siver June 18, 1946 

